The invention concerns a flowmeter system receiving liquids from stationary reservoirs onto tanker vehicles, in particular for milk, with a self-priming displacement pump followed by a deaerator with a venting valve above a float acting on it, the aerator being followed by a flowmeter in turn followed by a check valve.
Known metering systems of this kind suffer from the drawback that accurate volumetric control must be provided in the deaerator and hence accurate measurement values remain to be provided.
In these systems the float is connected by a float rod to the sealing member of the venting valve. After all the liquid has been passed, the displacement pump delivers air from the supply tank and presses this air into the deaerator. Thereby the liquid in the deaerator is delivered to the flowmeter until the float opens the venting valve of the deaerator.
This opening mechanism takes place in impulsive manner: the pressure building up in the upper region of the deaerator acts on the sealing member of the venting valve and keeps it closed until the liquid level in the deaerator drops below a specific level underneath the float's floating position. Hence the venting valve following the drop of the liquid level underneath the floating position is opened impulsively by the intrinsic weight of the float falling into the floating position, and thereupon the delivery of the liquid also comes to a stop impulsively.
Inaccuracies of measurement may occur if the magnitude of the drop by the deaerator's float is relatively large because the delivery of residual quantities may result in a post-delivery of liquid into the deaerator without the residual quantities sufficing to close the venting valve again. In this manner an imprecisely defined quantity is stored in the deaerator when delivery is shut off, and this amounts to inaccuracy.
Therefore the attempt must be made to minimize the drop.
On the other hand it is already known to quantify using relatively expensive electronic level controls in the form of pickups or the like.
These known systems however suffer from the drawback of the entailed apparatus complexity and furthermore that the milk delivered by the displacement pump tends to foam and hence the electric or electronic pickups provide inaccurate data. These problems are intensified when large flow rates especially of milk are involved, that is, when a high rate is required. These difficulties are enhanced in tanker vehicles when the reservoirs are at a relatively low position and therefore long intake lines are required.